The invention relates to an electric fan, in particular, for motor vehicles, comprising an electric drive motor, a fan wheel coupled with the drive motor, and an electronic control unit for controlling the drive motor.
Such electric fans are used, in particular, for cooling the drive units of a motor vehicle. Herein, a flow of air oriented substantially parallel to the axis of rotation of the fan wheel is generated by the fan wheel and directed, for example, at a radiator unit of the motor vehicle.
In order to achieve optimum cooling with as little energy as possible, the rotational speed of the fan wheel can be set in accordance with the respective cooling requirement. A control unit is normally used for this purpose. This is coupled with the drive motor and enables power-controlled operation of the drive motor. To this end, the control unit usually comprises a control circuit which generates a PWM signal, i.e., a pulse-width-modulated signal for controlling a power output stage, usually in the form of at least one FET output stage switch.
The control unit is usually connected via connection cables to the drive motor and arranged in a separate housing.
The object of the present invention is to make an electric fan of the kind mentioned at the outset structurally more simple and more cost-effective to assemble.
This object is accomplished with a fan of the generic kind in accordance with the invention in that the drive motor and the control unit are arranged in a common housing, and in that the housing has air vents for passage of a flow of cooling air generatable by the fan wheel, and a heat sink of the control unit is arranged at at least one air vent.
In accordance with the invention, the drive motor and the control unit form a common structural unit. This has the advantage that there is a significantly lower space requirement for the electric fan. Moreover, the electric fan is characterized by very good electromagnetic compatibility, as the control unit is arranged immediately adjacent to the electric motor and is surrounded together with it by a housing, with the aid of which an emission of electromagnetic interference is reliably preventable, as is also an influencing, in particular, of the electronic control unit by external electromagnetic radiation fields.
A further advantage of the design according to the invention is that a separate power supply line between the control unit and the drive motor is dispensed with. This power supply line is a main cause of electromagnetic interference. In addition, the compact design of the electric fan simplifies its handling and results in reduced susceptibility.
In accordance with the invention, provision is made for a flow of cooling air to be generatable by the fan wheel and to be passable through air vents of the housing. Heat dissipation is thereby ensured, so that in spite of the arrangement of the control unit and the drive motor in a common housing, reliable operation is guaranteed. Here provision is made in accordance with the invention for a heat sink of the control unit to be arranged at at least one air vent of the housing. The heat sink is thus directly exposed to the flow of cooling air generatable by the fan wheel, so that, in particular, the control unit does not undergo inadmissible heating during operation of the electric fan. The arrangement of the heat sink at an air vent of the housing makes it possible for the heat sink to be targeted with a flow of cooling air.
The arrangement of the at least one heat sink at an air vent of the housing also ensures that the flow of air generated by the fan wheel and oriented substantially parallel to the axis of rotation of the fan wheel remains uninfluenced by the cooling of the drive motor and the control unit. The flow of air can thus be used completely for cooling, for example, a drive unit of a motor vehicle without coming into contact with cooling elements of the drive motor or the control unit, which would result in a heating of the flow of air and hence in a reduction of the effective cooling performance of the fan. Moreover, the flow of air is not impeded, for example, deflected or partly faded out by cooling elements of the drive motor or the control unit. Instead, a separate flow of cooling air is used for cooling the control unit and the drive motor and like the flow of air provided for cooling external units, this is generated by the fan wheel but extends mainly inside the housing.
A particularly effective cooling of the housing interior is achievable in an advantageous design by the flow of cooling air having a flow section extending inside the housing and oriented substantially coaxially with the axis of rotation of the fan wheel. For example, provision may be made for the flow section oriented coaxially with the axis of rotation to pass virtually through the complete housing in the longitudinal direction thereof, so that both the electronic control unit and the drive motor are subjected to the flow of cooling air and thereby effectively cooled.
Alternatively and/or additionally thereto, provision may be made for the flow of cooling air to have a flow section inside the housing which is oriented substantially radially in relation to the axis of rotation of the fan wheel. This enables, in particular, guidance of the flow of cooling air inside the housing in such a way that the flow of cooling air enters and/or leaves the housing radially, to extend substantially coaxially with the axis of rotation of the fan wheel inside the housing.
It is of advantage for at least one heat sink to be arranged in the area of the radially oriented flow section of the flow of cooling air. In relation to the axis of rotation of the fan wheel this enables a particularly short structural design of the electric fan, as the heat sink can be arranged at the same level as the housing in relation to the axis of rotation.
In a particularly preferred embodiment of the fan according to the invention, provision is made for at least one heat sink to be arranged in the area of an air inlet opening through which the flow of cooling air is conducted into the housing interior. A particularly effective cooling of the heat sink and hence also of the electric components of the control unit thermally connected thereto is thereby ensured as the flow of cooling air is at its lowest temperature when entering the housing interior.
Alternatively and/or additionally thereto, provision may be made for at least one heat sink to be arranged in the area of an air outlet opening through which the flow of cooling air is conducted out of the housing interior. In such an embodiment, the flow of cooling air can first come into contact with the drive motor and the electric components of the control unit inside the housing and then pass over the heat sink at it exits from the housing.
As explained hereinabove, the heat sink is preferably arranged at an air vent which is arranged on a wall area of the housing surrounding the drive motor and the control unit in a circumferential direction.
It is expedient for the heat sink to have cooling fins, the surface normal of which is oriented substantially perpendicularly to the axis of rotation of the fan wheel. The cooling fins are preferably oriented parallel to one another and receive the flow of cooling air between them.
To ensure a particularly large contact surface between the drive motor and the flow of cooling air, provision is made in a preferred embodiment of the invention for at least one heat sink to be arranged at an air vent positioned adjacent to an end wall of the housing, and for the housing to have a further air vent in its end area remote from the end wall. This makes it possible for the flow of cooling air to pass through virtually the complete housing in the longitudinal direction thereof. Here it is particularly expedient for the heat sink to be arranged at an air inlet opening of the housing as this ensures a particularly effective cooling, in particular, of the control unit.
To generate the flow of cooling air, provision may be made for the fan wheel to generate a excess pressure or a negative pressure inside the housing by the housing being supplied with cooling air from the fan wheel or by a negative pressure being generated in the area of an air vent, which results in a suction current through the housing.
A design has proven particularly advantageous wherein the housing has an air outlet opening adjacent to the fan wheel, and the flow of cooling air in the area of this air outlet opening is settable in rotation around the axis of rotation of the fan wheel. During the rotational movement the flow of cooling air is subjected to a radially outwardly oriented force of inertia (centrifugal force), so that starting from the air outlet opening arranged adjacent to the fan wheel the cooling air is whirled outwardly at an incline. As a result of this, a negative pressure forms in the area of the air outlet opening, and to achieve a pressure compensation a suction current forms inside the housing in the direction towards the air outlet opening, which ensures effective cooling of both the control unit and the drive motor.
The rotational movement of the flow of cooling air can be created in a structurally particularly simple and cost-effective way by the fan wheel having lamellae arranged adjacent to the air outlet opening for moving the flow of cooling air around the axis of rotation. The lamellae are preferably oriented transversely to the direction of rotation of the fan wheel.
In order to create a particularly strong flow of cooling air inside the housing, it is of advantage for the air outlet opening to form an annular gap oriented coaxially with the axis of rotation of the fan wheel. This makes it possible to conduct the flow of cooling air out of the housing interior with uniform distribution over the entire extent of the housing, thereby enabling all areas of the housing interior to be uniformly cooled.
The housing can, for example, comprise a preferably U-shaped housing pot and a cover-type base plate, with the annular gap being delimited, on the one hand, by the housing pot and, on the other hand, by the base plate. Here it is particularly advantageous for the housing pot and the base plate to be held so as to be rotatable relative to each other. For example, provision may be made for the housing pot to be mounted for rotation on the base plate and for the fan wheel to be held on the housing pot. Such a design has proven its worth, in particular, when an electronically commutated fan motor is used as drive motor. Here the housing pot forms a magnetic loopback for permanent magnets secured inside the housing on the housing pot, and the housing pot also forms a hub for the fan wheel, which is rotationally fixedly held on the housing pot and surrounds the housing pot in a circumferential direction. The rotation of the housing pot results in the cooling air flowing through the housing in the area of the annular gap being set in rotation, and as a result of the centrifugal force thus created, the flow of cooling air in the area of the annular gap between the housing pot and the base plate is whirled outwards at an incline. A negative pressure is thus generated in the area of the annular gap. For pressure compensation, air inlet openings can, for example, be provided in a bottom wall of the housing pot and/or in the area of the base plate so as to form a flow of cooling air which passes through the housing interior.
The electronic control unit usually comprises a large number of electronic components secured to a printed circuit board. The printed circuit board is preferably arranged inside the housing such that the flow of cooling air passes over at least a partial area of the printed circuit board. It is of particular advantage for the printed circuit board to be arranged so as to be oriented transversely to the axis of rotation of the fan wheel in the area of a radial flow section of the flow of cooling air. Provision may, for example, be made for the printed circuit board to be oriented parallel to an end wall of the preferably cylindrical housing.
A particularly effective cooling of the control unit can be ensured by the printed circuit board being held on the heat sink, which extends into an air vent of the housing. Here it is expedient for the printed circuit board to be of ring-shaped design, with the heat sink held at the outer edge of the printed circuit board. In such an embodiment, the flow of cooling air can be supplied directly to the heat sink arranged at the outer edge of the printed circuit board, and as the printed circuit board is thermally coupled with the heat sink, a reliable cooling of the printed circuit board and the electronic components of the control unit attached thereto is thereby achievable.
The following description of two preferred embodiments of the invention serves in conjunction with the drawings to explain the invention in greater detail.